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The Return of Big Stadium Events: Is the Reward Worth the Risk?

April 16, 2021 | Article No. 76

The Return of Big Stadium Events: Is the Reward Worth the Risk?

April 16, 2021 | Article No. 76


Mohit Bhandari MD, PhD

Joseph Silburt PhD

“Let’s play ball”, April 1 marked opening day for the 2021 major league baseball season, and for many, the first vestiges of a return to normalcy. This year’s opening day was particularly special, because a limited number of fans were allowed back in the stadium to watch the game in person. However, as many countries around the world are experiencing a third wave of COVID-19, the question remains as to whether now is the time to begin re-opening. In this insight, we will explore the question, should we allow fans in the stadiums, and what is the risk of spreading COVID-19.


  • Well over half of professional NHL and NBA teams, and 100% of MLB teams have announced plans to open stadiums to fans at least in some capacity.

  • The precautionary principle by itself does not justify the closure of stadiums, and COVID-19 policies as much as possible should be evidence based to ensure that they are as unrestrictive as possible.

  • A limited number of observational studies suggest that fans attending games, particularly with crowd sizes exceeding 20,000 lead to an increased community spread of COVID-19.

  • Despite this, some experts and simulation studies have suggested that precautionary measures, including physical distancing, sanitation, and mask wearing can substantially reduce the risk.

  • The predicate that fans will dutifully adhere to COVID-19 precautionary measures may be misplaced.

  • COVID-19 vaccine passports may represent a middle ground to allow vaccinated persons to return to begin a return to normalcy. However, the ethics of COVID-19 vaccines passports remain dubious in practical terms, particularly with respect to ensuring equity for marginalized populations.

Current openings

Exhibit 1: Currently playing professional sports leagues and policies on in person attendance.

Scroll Horizontally >

League Partially Open to Fans Total Teams
MLB 30§ 30
NHL 18 31
NBA 23 31
Bundesliga 0* 18

*Teams were allowed to host up to 20% stadium capacity in September 2020, which has since been revoked.

§Only 1 team, the Texas Rangers, have no attendance restrictions.

Building of the decision of the NFL to re-allow fans in the stadiums, in concert with local governments, the MLB made the decision to allow for all teams to begin to allow fans back into the stadiums, which in the vast majority of cases are open air. Currently, most MLB times have applied to allow between 20-30% stadium capacity, translating to between 10,000 to 15,000 fans.  Bucking this trend, on April 5, 2021, the Texas Rangers heralded their home opener to a raucous capacity crowd of 40,000 fans having not placed any restrictions on crowd sizes (1). In line with this trend, the 18 NHL and 23 NBA teams, who play in closed air stadiums, have begun to allow a small number of fans back into the stands. While the Bundesliga, the German soccer league, initially allowed for a return to 20% stadium capacity in September 2020, this has since been cancelled due to the recent increases in COVID-19 cases (2). It remains far too early to understand the real-time impact of stadium re-openings on the community spread of COVID-19, nevertheless, we can yet explore the science to better understand the risk.

“The precautionary principle justifies taking preventive measures even though scientific consensus may not yet have been reached. It should be noted, however, that the [precautionary principle] does not supplant the principle of proportionality. This includes necessity, proportionality, the need for continuous review and updating as science improves, and the need for transparency and excellence in science.” (3) 

Klaus Meßerschmidt, 2020

A primer: The precautionary principle and the ethics of risk

Germane to the question, “should we allow for fans in stadiums?”, is the precautionary principle, a moral compass, which has guided much of public policy in the wake of the COVID-19 pandemic (3). In brief, the precautionary principle states that in situations of unknown risk, it is prudent to err on the side of caution, particularly when the stakes are high. The COVID-19 pandemic marks possibly the most prominent example of applying the precautionary principle to public policy, where to safeguard against another 1918 influenza pandemic, many governments overnight imposed expansive lock downs that limited the mobility and economic activity of its citizens (3). For many in health care professions, the logic behind the precautionary principle may feel natural and intuitive, as it is well aligned with a general inclination to first do no harm, and preserve life above all else. It is therefore not surprising that there are no shortage of medical opinions and calls to action by health care practitioners in support of generally strict lockdown and physical distancing measures (4). In general, this intuition has proven correct, as post-mortem analyses of lockdown and physical distancing policies have affirmed them to be necessary and effective at reducing the spread of COVID-19 (5). 

However, ultimately in discussing COVID-19 policy, it is prudent to recognize that restrictive policies also have significant consequences. As illustrated in our recent OE insight , COVID-19 policies place burdens on patient treatment, which has resulted in a significant backlog of surgeries, and a spike in opioid dependence. Outside of the clinic, the COVID-19 lockdown has resulted in a significant increase in depression and sedentary lifestyles, which represent important risk factors for disease (e.g., cardiovascular disease, stroke) (6). Lockdown-associated economic losses further represent a pervasive and important risk factor for disease. Indeed, the 2008 global recession was responsible for the deaths of at least 260 000 excess cancer-related deaths across Organisation for Economic Co-operation and Development countries (7). Thus, precaution must be balanced with proportionality, to ensure that restrictions are dutifully targeted to be the least restrictive that they can be (3,8).

Thus, as an opening context for evaluating the wisdom of opening stadiums, it is important to evaluate a more nuanced balance of risks and benefits of this decision (3).

“The increased spikes in COVID-19 cases and rates among those games attended by fans, particularly for large crowds of over 20,000 suggest that return to sporting and other mass gathering events should be handled with extreme caution and may indeed be premature. Within the context of large-scale sporting events, a more moderate, phased-in approach may be required to initially limit crowds until a sufficient level of herd immunity is reached.” (14)

Kurland et al. 2021

How effective can COVID-19 stadium precautions be at stopping the spread of COVID-19?

In quantifying the risk associated with large crowds, it must first be recognized that the nature of studying the spread of COVID-19 is an incredibly difficult task. Unlike in a clinical setting, it is not feasible to conduct a randomized controlled trial to test an acceptable crowd size. Thus, most evidence is derived from observational trends, and simulation studies, or extrapolated from small scale laboratory tests. This should be considered a major caveat when evaluating the current best assessments and expert opinions on the magnitude of the risk. 

At the heart of most stadium re-opening plans is the concept of physical distancing, where, limiting the proximity of persons to each other can effectively limit the spread of the virus. A systematic review on the effects of physical distancing on the risk of infection for MERS, SARS, and COVID-19 found that physical distancing of 1m or more reduced the odds of infection by nearly 5-fold (9) (read the ace report) . Contrasting this view, in their high-profile perspective Jones et al. argue that the 1-2m physical distancing rule is largely based on old science and that the evidence to support 2m as a particularly safe threshold distance is weak (10). For example, aerosolized viruses can comfortably travel beyond 7-8m, especially when projected through yelling or other vigorous evulsions (such as fan cheering) and are thought to be stable as airborne aerosols for up to 16 hours (11,12). 

As it pertains to real world settings, even in well-ventilated stadiums, physical distancing alone seems to be insufficient. Analyzing the spread of COVID-19 following soccer matches in the United Kingdom in the first few months of the pandemic Olczak et al. suggested that even at 20% capacity, stadiums likely significantly contributed to the spread of COVID-19 (13). A recent analysis of American football games similarly found an increased risk of community COVID-19 spread associated with the presence of fans at football games, despite the precautions put in place, particularly when crowd sizes exceeded 20,000 persons (14). However, crowd sizes of 5000 or less resulted in no measurable increase in the spread of COVID-19 (14). In part, the added risk of more people can be attributed to the fact that there is so much more to a sports event than sitting and watching the game. Even with properly spaced seats, there is a high risk for fans to congregate at concession stands and other common areas. Bathrooms in particular have been shown to be hotbeds for aerosolized COVID-19 particles (15), and are a major area of concern (16). 

Yet, with sufficient precautions put in place, there is some evidence that stadiums can be de-risked. A recent preprint study which aimed to simulate the risk of COVID-19 transmission at a concert estimated that transmission could be maintained to “low” levels, measured at 10 cases resulting from the event, if adequate ventilation and proper hygiene was maintained (17). Similarly, in modeling the risk of COVID-19 spread at the 2021 Tokyo Olympic games 2021, basic preventative measures, including physical distancing, sanitation, ventilation, face masks, headwear (e.g., hats), handwashing, and partitioning fans to separate locations in the stadium, promised to reduce the spread of COVID-19 by 99% (18). Particularly for open air stadiums, such precautions have precipitated some experts to endorse the opening of sports stadiums. As Dr. Dean Winslow of Stanford Health Centre told ABC News about the opening of baseball stadiums, “I think it’s a minimal degree of risk with the limitations that have been proposed” (19). However, key to this prescription was that crowd sizes were kept well below stadium capacity.  Echoing this sentiment, Dr. Emily Landon of the University of Chicago explained that stadium capacity could be progressively opened in stages, stating, “If the cases keep going down, there is no reason to hesitate to have people, especially masked people, gather at these events” (19).

Beyond the venue itself, sports events have a life of their own which can risk the spread of COVID-19. Before the game fans engage in tailgating parties where they hang out in the parking lot, share food, and drink beer in ritualistic preparation to cheer on their team. Local bars and restaurants likewise see a high volume of fans who are trying to prepare for, or partake in the sports experience. It is no secret that high mobility, and exposure to dense areas has been a major instrument in the spread of COVID-19 (5). Indeed, a recent preprint studying the Bundesliga, the German soccer league, found that through increasing local mobility of fans, soccer events in Germany led to an increase in the incidence of COVID-19 (20). Even if stadiums can manage and maintain physical distancing and sanitation protocols at a high level, there is no guarantee that these measures could be maintained for all ancillary elements of the sports events. 

“Fans initially followed the mask rules but only about 50 per cent of them were still wearing the masks during the middle innings, the AP reports. Stadium staff were not stopping maskless fans.”(1)

Josh Elliot, Global News, 2021.

The elephant in the room: conspiracies and compliance

A key element to proposals for re-opening is that participants adhere to strict physical distancing and mask wearing guidelines. This in turn reveals perhaps the Achilles heel of any plan to re-open: people.

In following the news, you might have noticed that COVID-19 safety procedures, in particular mask-wearing, has been the subject of controversy, and in some cases, conspiracies, with many proclaiming their defiance to wearing masks. However, how widespread is this problem really? Adherence to mask wearing is difficult to measure, and certainly is likely to change based on geography, and shifts in public opinion. While the problem of not wearing masks likely exists to some degree all over the world, most studies have focused on the United States. One survey indicated that Americans reported wearing masks to supermarkets ~90% of the time. However, in other indoor settings, such as entering a house, attending large gatherings, or entering a bar, less than 50% of respondents reported wearing masks (21). Moreover, 1 in 10 respondents saw mask-wearing as dangerous to their health, or a political statement (21). Survey data by its nature is subject to self-reporting bias. Thus, Haischer et al. aimed to understand mask wearing compliance through directly observing nearly 10,000 shoppers as they entered grocery stores at several locations across Wisconsin, USA. In line with the notion that compliance is less than stellar, only 41% shoppers entering the store wore a mask. While such individual studies should not be construed to mean that a lack of mask wearing is a problem everywhere, it should give us pause with assuming that current mask wearing policies are effective and working as intended. Indeed, reports from the Texas Rangers home opener reported a notable dearth of mask wearing (1). 

The reasons for non-compliance with COVID-19 policies is likewise difficult to determine, but political affiliation is known to be a contributing factor (22). Moreover, a study conducted in Germany determined that requiring citizens to wear masks through a mandate, was far more effective than asking them to do it on a voluntary basis (23). Thus, in aiming to re-open businesses and stadiums, policy makers would do well to send clear signals on the necessity of physical distancing and mask wearing procedures as instruments to permit safety in stadiums.

“Sport has the power to change the world. It has the power to inspire. It has the power to unite people in a way that little else does." (24)

Nelson Mandela, 2000

Public and private interests for re-opening

Despite all of the challenges associated with re-opening stadiums during the COVID-19 pandemic, it is important to underscore that not re-opening also has consequences. Across the four major sports in North America (i.e, Hockey, Baseball, Football, Basketball) revenue losses due to COVID-19 interruptions have exceeded $14.1 billion, and the cost to local sports economies are likely to be significantly higher (25). However, beyond the economics, sports provide numerous intangible benefits to cities and spectators. Just as the NBA’s decision on March 11, 2020 to postpone the remainder of the 2020 NBA served to signal the seriousness of the COVID-19 threat, the return of sports as usual may herald a return to normalcy. In a recent poll of those who attended a live sports event, 85% reported feeling safe, and respondents reported, "a massive lift to mental health" and "a sense of community" when attending the events (26). In line with this sentiment, the majority of ticket prices for the Texas Rangers home opener available on secondary resale markets exceeded $100, an indication of significant demand (26).

By contrast, others argue that the notion that re-opening stadiums will boon our collective mental health as largely superficial (27). Indeed, a more general poll of Americans that asked whether Americans were ready to attend live sports were equally split between those who were and were not willing (28). 

Nevertheless, it is important to recognize the central role of sports for many, and the impetus many feel to move past the limitations placed by the COVID-19 pandemic.

“The public health principle of least infringement states that to achieve a public health goal, policy makers should implement the option that least impairs individual liberties.” (29)

Tasnime et al. 2021

Covid passports: ethical and practical issues

So how about those who have already been vaccinated against the COVID-19 virus? given their elevated level of protection, can’t stadiums be safely opened to those at low risk of infection? This has been the thinking for many – not only can fans in a limited degree begin to attend sports events, but sports would also serve to incentivize the population to get vaccinated (30). Indeed, in part to reward their hard work, and in part to get fans back in the stands, sports teams like the Charlotte Hornets welcomed front line health care workers to watch their NBA home opener (31). More generally, proposals like these, termed immunity, or vaccine passports have been pitched as a way to begin to re-open the economy, and reinstate travel across borders. Currently a number of countries, notably the United Kingdom, have moved to test the feasibility and effectiveness of vaccine passports (32). 

This, however, has not come without significant controversy. The ethics and efficacy of vaccine passports is currently front and center of COVID-19 public policy debates. Influential publications including NEJM, JAMA, the BMJ and Science, among others, have explored the complex issue of vaccine passports, and have reached somewhat different conclusions (8,29,30,33–35). The benefits of vaccine passports are clear, as they allow a subset of the population (i.e., those vaccinated) more freedoms, and can hopefully kickstart a return to normalcy (35). The question remains as to whether they are ethical. 

Based on guidance from the World Health Organization, public policies to combat COVID-19 should be as unrestrictive as possible while maintaining efficacy (8). In this vein, many see a vaccine passport – wherein those who are vaccinated can freely move – as less restrictive than physically restricting the movements of all residence in a society (8). Given that vaccine passports afford more freedoms than the alternative, they are therefore not inherently impermissible (29,35). Indeed, the WHO already supports the use of vaccine passports for Yellow Fever when accessing certain high risk countries (29). Persad and Emmanuel further argue that prejudice based on vaccination status is ethically acceptable and should be distinguished from other forms of unequal treatment because the means by which people are being prejudiced, i.e., their risk for contracting and spreading COVID-19, is based on rational evidence (35). 

On the other hand, there are serious concerns about inequities and the feasibility of implementation (8,29,30,33–35). Moreover, for some, vaccine passports serve as evidence of a tyrannical or overbearing government. As with any public policy there is always a significant risk for unintended consequences. There is the deep rooted concern that COVID-19 passports may stigmatize and isolate members of society who chose not to, or are unable, to receive a vaccine (30,35). As a general rule, laws that require proof of identification can disproportionately impact those of low socioeconomic status, who may have less means, or less time (e.g., cannot take time off work) to acquire identification (35). There are similar concerns about vaccines and vaccine passports which may be inaccessible for marginalized populations, who, in fact, require them the most (29,30,34,35). The use of vaccine passports are further complicated by the emergence of new COVID-19 strains for which the efficacy of vaccines, and therein the premise of vaccine passports, remain unclear (30,35). 

Nevertheless, it is prudent to understand if we can identify specific cases where vaccine passports may be permissible. Importantly, requiring vaccination for access to essential (often government run) services such as hospitals or schools effectively serves as a mandate for vaccination, which has significant risks for excluding many, and therefore should be pursued only with extreme caution and need (i.e., generally not pursued) (30,36). By contrast, there is nothing necessarily preventing private companies such as airplane businesses or sports teams from implementing vaccine passport requirements for accessing their goods and services. Thus, absent any decisions from policy makers vaccine passports may still become a reality (30,33). Indeed, Duke university among several other educational institutions recently announced that all students attending in the fall would need to be vaccinated (37). In this respect, government oversight and partnership is likely required to address important logistical issues, including that vaccine passports are accurate, and standardized across borders, and protect the privacy of citizens.

Thus, despite the many complex issues, most perspectives from the medical literature conclude that vaccine passports, while not inherently unethical, are subject to many practical pitfalls which could make them unethical (29,30,33,34,36). This highly nuanced conclusion underscores that the answer to this question is not objectively obvious and will be evaluated by each individual country in accordance with the available evidence, popular sentiments, and their needs. Indeed, a recent representative national poll conducted in the US identified that the country was split 50/50 among those who supported and did not support vaccine passports – leading to the prognostication that the US are unlikely to adopt a wide reaching vaccine policy (30). By contrast, the United Kingdom is moving ahead with a vaccine passport policy (32). 


In revisiting the central question of this insight, “is it safe to re-open to stadiums?”, the answer ultimately depends on context, and what is considered an acceptable level of risk tolerance. From a purely scientific basis, publicly available studies on observational data suggest that live stadium sports will lead to some additional community spread of COVID-19. However, this risk can be reduced if crowd sizes are limited and proper safety procedures put in place, especially for open air stadiums. This conclusion is highly caveated by the fact that it is incredibly difficult to link stadium events to the community spread of COVID-19. Stadium re-openings are further predicated on the willful and active adherence of participants to strict COVID-19 safety protocols, a requirement which is by no means guaranteed. Regardless, if the limits to spreading COVID-19 are “minimal”, live sports serves for many as an important public good and return to normalcy, and that has value. One possible middle ground is to use vaccine passports, wherein those who have been fully vaccinated can attend sporting events. However, the ethics of vaccine passports remain unclear, and they likely will not be widely used in the US, where live sports have returned. Ultimately, COVID-19 public health policy is fraught with uncertainty and constructed based on the judgement and tolerance of individual jurisdiction. Regardless, the pandoras box of a return to large stadium events has been opened, and for better or worse, the next few weeks will prove an instrumental real-world test case on whether stadium sports can be conducted safely.


Mohit Bhandari MD, PhD

Dr. Mohit Bhandari is a Professor of Surgery and University Scholar at McMaster University, Canada. He holds a Canada Research Chair in Evidence-Based Orthopaedic Surgery and serves as the Editor-in-Chief of OrthoEvidence.

Joseph Silburt PhD

Joey is a data scientist at OE. He received a PhD in Laboratory Medicine and Pathobiology from the University of Toronto, and a B. Sc. from the University of Calgary.


  1. Elliot J. 40,000 fans pack into Texas Rangers stadium despite COVID-19 threat [Internet]. Global News. 2021 [cited 2021 Apr 14]. Available from: https://globalnews.ca/news/7740355/texas-rangers-stadium-fans-opening-day/
  2. Uersfeld S. Bundesliga boost as home fans allowed back for new season [Internet]. ESPN. 2020 [cited 2021 Apr 14]. Available from: https://www.espn.com/soccer/german-bundesliga/story/4182225/bundesliga-boost-as-fans-allowed-back-for-new-season
  3. Meßerschmidt K. COVID-19 legislation in the light of the precautionary principle. Theory Pract Legis [Internet]. 2020 Sep 1 [cited 2021 Apr 5];8(3):267–92. Available from: https://www.tandfonline.com/action/journalInformation?journalCode=rtpl20
  4. Greenhalgh T. Covid-19: An open letter to the UK’s chief medical officers. BMJ Opinion Blog [Internet]. 2020 [cited 2021 Apr 5]; Available from: https://blogs.bmj.com/bmj/2020/09/21/covid-19-an-open-letter-to-the-uks-chief-medical-officers/
  5. Chang S, Pierson E, Koh PW, Gerardin J, Redbird B, Grusky D, et al. Mobility network models of COVID-19 explain inequities and inform reopening. Nature [Internet]. 2021 Jan 7 [cited 2021 Apr 7];589(7840):82–7. Available from: https://doi.org/10.1038/s41586-020-2923-3
  6. Hall G, Laddu DR, Phillips SA, Lavie CJ, Arena R. A tale of two pandemics: How will COVID-19 and global trends in physical inactivity and sedentary behavior affect one another? [Internet]. Vol. 64, Progress in Cardiovascular Diseases. W.B. Saunders; 2021 [cited 2021 Apr 14]. p. 108–10. Available from: /pmc/articles/PMC7194897/
  7. Maruthappu M, Watkins J, Noor AM, Williams C, Ali R, Sullivan R, et al. Economic downturns, universal health coverage, and cancer mortality in high-income and middle-income countries, 1990–2010: a longitudinal analysis. Lancet [Internet]. 2016 Aug 13 [cited 2021 Apr 5];388(10045):684–95. Available from: http://www.thelancet.com/article/S0140673616005778/fulltext
  8. Voo TC, Reis AA, Thomé B, Ho CWL, Tam CC, Kelly-Cirino C, et al. Immunity certification for COVID-19: Ethical considerations. Bull World Health Organ [Internet]. 2021 [cited 2021 Apr 9];99(2):155–61. Available from: http://dx.doi.org/10.2471/BLT.20.280701
  9. Chu DK, Akl EA, Duda S, Solo K, Yaacoub S, Schünemann HJ, et al. Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis. Lancet [Internet]. 2020 Jun 27 [cited 2021 Apr 7];395(10242):1973–87. Available from: https://doi.org/10.1016/
  10. Jones NR, Qureshi ZU, Temple RJ, Larwood JPJ, Greenhalgh T, Bourouiba L. Two metres or one: what is the evidence for physical distancing in covid-19? BMJ [Internet]. 2020 Aug 25 [cited 2021 Mar 31];370:m3223. Available from: http://dx.doi.org/10.1136/bmj.m3223http://www.bmj.com/
  11. Bourouiba L. Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID-19 [Internet]. Vol. 323, JAMA - Journal of the American Medical Association. American Medical Association; 2020 [cited 2021 Apr 7]. p. 1837–8. Available from: https://www.cdc.gov/coronavirus/2019-ncov/
  12. van Doremalen N, Bushmaker T, Morris DH, Holbrook MG, Gamble A, Williamson BN, et al. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. N Engl J Med [Internet]. 2020 Apr 16 [cited 2021 Apr 7];382(16):1564–7. Available from: http://www.nejm.org/doi/10.1056/NEJMc2004973
  13. University of Reading. Even 80% empty stadiums linked to higher Covid-19 cases and deaths [Internet]. University of Reading. 2020 [cited 2021 Apr 7]. Available from: https://www.reading.ac.uk/news-and-events/releases/PR847106.aspx
  14. Kurland J, Piquero A, Leal WE, Sorrell EM, Piquero NL. COVID-19 Incidence Following Fan Attendance: A Case Study of the National Football League 2020-2021 Season. SSRN Electron J [Internet]. 2021 [cited 2021 Apr 13]; Available from: https://www.ssrn.com/abstract=3805754
  15. Liu Y, Ning Z, Chen Y, Guo M, Liu Y, Gali NK, et al. Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals. Nature [Internet]. 2020 Jun 25 [cited 2021 Apr 6];582(7813):557–60. Available from: https://doi.org/10.1038/s41586-020-2271-3
  16. Parker J, Boles C, Leleck O, Buerger A, Egnot N, Sundermann A, et al. Advancing toward normal operations for arenas and stadiums. Toxicol Ind Health [Internet]. 2020 Sep 1 [cited 2021 Mar 31];36(9):718–27. Available from: http://journals.sagepub.com/doi/10.1177/0748233720964651
  17. Moritz S, Gottschick C, Horn J, Popp M, Langer S, Klee B, et al. The risk of indoor sports and culture events for the transmission of COVID-19 (Restart-19) [Internet]. medRxiv. medRxiv; 2020 [cited 2021 Mar 31]. p. 2020.10.28.20221580. Available from: https://doi.org/10.1101/2020.10.28.20221580
  18. Murakami M, Miura F, Kitajima M, Fujii K, Yasutaka T, Iwasaki Y, et al. COVID-19 risk assessment at the opening ceremony of the Tokyo 2020 Olympic Games. Microb Risk Anal. 2021 Mar 21;100162. 
  19. Pereira I. Baseball stadiums are reopening this spring. What’s the COVID risk? [Internet]. ABC News. 2021 [cited 2021 Apr 13]. Available from: https://abcnews.go.com/Sports/baseball-stadiums-reopening-spring-covid-risk/story?id=76327225
  20. Fischer K. Thinning out Spectators: Did Football Matches Contribute to the Second COVID-19 Wave in Germany? by Kai Fischer :: SSRN. SSRN [Internet]. 2021 [cited 2021 Apr 6]; Available from: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3793379
  21. Darling J, Thomas K, Kapteyn A, Perez-Arce F. Vast Majority of Americans Support Wearing Masks, But a Deeper Look at Behavior Reveals Troubling Lack of Adherence – USC Schaeffer [Internet]. The Evidence Base. 2020 [cited 2021 Mar 31]. Available from: https://healthpolicy.usc.edu/evidence-base/vast-majority-of-americans-support-wearing-masks-but-a-deeper-look-at-mask-wearing-behavior-reveals-troubling-lack-of-adherence-to-social-distancing-recommendations/
  22. Grossman G, Kim S, Rexer JM, Thirumurthy H. Political partisanship influences behavioral responses to governors’ recommendations for COVID-19 prevention in the United States. Proc Natl Acad Sci U S A [Internet]. 2020 Sep 29 [cited 2021 Apr 7];117(39):24144–53. Available from: https://www.pnas.org/content/117/39/24144
  23. Betsch C, Korn L, Sprengholz P, Felgendreff L, Eitze S, Schmid P, et al. Social and behavioral consequences of mask policies during the COVID-19 pandemic. Proc Natl Acad Sci U S A [Internet]. 2020 Sep 8 [cited 2021 Apr 7];117(36):21851–3. Available from: www.pnas.org/cgi/doi/10.1073/pnas.2011674117
  24. Mandela N. Nelson Mandela: ‘Sport has the power to change the world’ Laureus Lifetime Achievement Award - 2000 [Internet]. Speakola. 2000 [cited 2021 Apr 14]. Available from: https://speakola.com/sports/nelson-mandela-laureus-lifetime-achievement-award-2000
  25. Birnbaum J. Major Sports Leagues Lost Jaw-Dropping Amount Of Money In 2020 [Internet]. Forbes. 2021 [cited 2021 Apr 11]. Available from: https://www.forbes.com/sites/justinbirnbaum/2021/03/06/major-sports-leagues-lost-jaw-dropping-amount-of-money-in-2020/?sh=6eff47f669c2
  26. Sergent J, Lacques G, Stucka M. MLB opening day: COVID-19 infections rise as stadiums open to fans [Internet]. USA Today. 2021 [cited 2021 Apr 13]. Available from: https://www.usatoday.com/in-depth/sports/2021/03/31/mlb-opening-day-covid-19-infections-rise-stadiums-open-fans/7020066002/
  27. Wagner J. Can Sports Help Heal a Country? Some Fans Don’t Buy the Emotional Pleas [Internet]. The New York Times. 2020 [cited 2021 Apr 11]. Available from: https://www.nytimes.com/2020/05/16/sports/baseball/coronavirus-sports-comeback.html
  28. Maese R, Clement S. Poll: Americans have coronavirus concerns over attending sports in person - The Washington Post [Internet]. The Washington Post. 2021 [cited 2021 Apr 11]. Available from: https://www.washingtonpost.com/sports/2021/03/31/sports-fans-live-attendance-poll/
  29. Osama T, Razai MS, Majeed A. Covid-19 vaccine passports: access, equity, and ethics. BMJ [Internet]. 2021 Apr 1 [cited 2021 Apr 9];373:n861. Available from: http://www.ncbi.nlm.nih.gov/pubmed/33795260
  30. Hall MA, Studdert DM. “Vaccine Passport” Certification — Policy and Ethical Considerations. N Engl J Med [Internet]. 2021 Mar 31 [cited 2021 Apr 9];NEJMp2104289. Available from: http://www.nejm.org/doi/10.1056/NEJMp2104289
  31. Perley S. One Year Later, Hornets Kickoff Return to Fans by Welcoming Novant Workers to Spectrum Center [Internet]. NBA.com. 2021 [cited 2021 Apr 8]. Available from: https://www.nba.com/hornets/one-year-later-hornets-kickoff-return-fans-welcoming-novant-workers-spectrum-center
  32. Hui S. U.K. to test COVID-19 passports at mass gatherings in coming weeks - National | Globalnews.ca [Internet]. The Associated Press. 2021 [cited 2021 Apr 14]. Available from: https://globalnews.ca/news/7737790/uk-vaccine-passport-test-coronavirus/
  33. Wilson K, Flood CM. Implementing digital passports for SARS-CoV-2 immunization in Canada. Can Med Assoc J [Internet]. 2021 Apr 6 [cited 2021 Apr 9];193(14):cmaj.210244. Available from: www.iata.org/en/programs/passenger/travel-pass/
  34. Dye C, Mills MC. COVID-19 vaccination passports. Science (80- ) [Internet]. 2021 Mar 19 [cited 2021 Apr 9];371(6535):1184–1184. Available from: http://science.sciencemag.org/
  35. Persad G, Emanuel EJ. The Ethics of COVID-19 Immunity-Based Licenses (“Immunity Passports”) [Internet]. Vol. 323, JAMA - Journal of the American Medical Association. American Medical Association; 2020 [cited 2021 Apr 8]. p. 2241–2. Available from: https://jamanetwork.com/
  36. Mello MM, Silverman RD, Omer SB. Ensuring Uptake of Vaccines against SARS-CoV-2. N Engl J Med [Internet]. 2020 Oct 1 [cited 2021 Apr 9];383(14):1296–9. Available from: http://www.nejm.org/doi/10.1056/NEJMp2020926
  37. Dickler J. Covid vaccines increasingly mandatory at colleges this fall [Internet]. CNBC. 2021 [cited 2021 Apr 14]. Available from: https://www.cnbc.com/2021/04/12/covid-vaccines-increasingly-mandatory-at-colleges-this-fall.html

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